Ask the Vet: Tendons with Nick Roe

What have Saintly, Kibah Tic Toc, It’s A Knockout and Custom Made all got in common. Winners? Yes. Very fast gallopers? Yes. Stayers? Yes. But apart from that they have all returned successfully after tendonitis of the Flexor digitorum superficialis.

Our management of ‘bowed’ tendons has changed over the last fifty years. Gone (hopefully) are the days of pinfiring the tendon and turning them out and forgetting about them for twelve months, and then when you bring them back in only fifty percent of them would stand up to a preparation or two.

Nowadays, with ultrasound, advancements in physio techniques, but most of all the use of controlled and graded exercise, you can win a gold medal or two (in Matt’s case, one for each tendon).

A tendon is a bundle of elastic fibres, made up mainly of collagen, which attaches a muscle to a bone. Ligaments are similar structures but go from bone to bone. Their structure is comparable to a bungy rope, that is a whole heap of elastic parallel fibres make up the overall tendon. Now when fibres tear then that is called a strained tendon. Tearing of fibres sets up inflammation within that tendon and that is called tendonitis.

A ‘bow’ in the tendon describes the shape or the profile seen when the tendonitis of the superficial digital flexor tendon, is very severe or chronic.

Just because you have a few dodgy strands in your bungy doesn’t mean that you can’t use that bungy, or that the bungy is obviously broken. But, if fat boys keep using that bungy then a few torn fibres will become a few more then a lot, until the thing snaps all the way through.

It is the same with mild tendon strains. The initial signs are only minor, a little bit of heat, swelling and pain on palpation, and usually no sign of lameness. It is quite a common mistake of riders and trainers to notice the heat and swelling, but because the horse is not sore then they continue work as per usual. This usually leads to further fibre tearing and a worsening of the inflammatory response until finally help is sought – usually a fortnight or so late.

Diagnostic ultrasound is extremely useful in evaluating tendon injuries. You don’t need an ultrasound necessarily to diagnose tendonitis, once you’ve seen a few they are pretty easy to diagnose. But the ultrasound machine gives you a very good picture of the exact location, size and severity of the tear. It is therefore very useful in monitoring the progress of healing of the tear.

So if your prize pony has strained a tendon why do so many people consider it a curse? Two reasons. Firstly tendon injuries take a long time to heal and secondly, depending upon management, there is a reasonably high rate of recurrence.
One of the main reasons they are slow to heal is the poor blood supply to tendons. Next time you are chewing on the gristly tendon of a lamb shank, take the time to look for blood vessels in that tendon. If you’ve got really good eyes you’ll see only one little blood vessel in the very centre of the tendon. This means that all the supplies for cell division and tendon repair come from one tiny little vessel or diffuse in from surrounding tissues. The fibres that are torn are replaced with a different type of collagen to the original collagen. The replacement collagen (scar tissue) is not as stretchy as the original, so going back to bungy jumping, its like repairing a slight tear in the bungy rope with strands of bailing twine. Obviously this is going to be the weak link in the structure.

THERAPY
1: Acute Stage (0 – 48 hrs)
The main goal of the initial therapy is to minimise inflammation. Inflammatory products cause more damage and more fluid or oedema to build up, the more of this, and the longer it hangs around, the more scar tissue is laid down.

Ice Cold therapy for twenty to thirty minutes four times a day has a very good anti-inflammatory effect.

Bandaging A good pressure bandage with plenty of cotton wool applies counter pressure to any swelling that is present and keeps the tissue planes collapsed to prevent the undesirable build up of fluid within the tendon.

Rest Box rest is essential to limit any further damage.

Pharmacological Non-steroidal anti-inflammatories (such as bute and finadyne) at the higher dose rates are essential to limit the initial inflammatory response. Ultra short acting corticosteroids can be used in the first forty-eight hours only. Corticosteroids are very potent anti-inflammatories but if used later than this they will slow down the rate of healing. Hyaluronic acid, BAPN and PSGAG’s have been injected in and around the lesions but there is insufficient proof of their benefits.

2: Sub-Acute Stage (Day 2 – 21)
The main aims of this stage are to stop the spread of inflammation to normal tendon, reverse the acute inflammation, minimise permanent damage and start the repair process to maximise orderly and functional tendon repair.

Hot & cold therapy. This can be achieved by using sweat wraps in between ice treatments. A good sweat wrap is to put a layer of glad wrap under your pressure bandage. Continue this for up to six days. The idea being to remove as much of the tissue fluid before the fibroproliferative phase begins. Once this phase begins it becomes more and more difficult to remove this fluid as it is converted into scar tissue.

NSAID’s: Bute should not be continued for more than three weeks.

Laser therapy and Therapeutic ultrasound: Both are very good at increasing the rate of healing and limiting the amount of scar tissue. It is well worth while to source either of these machines and hire them for at least three months.

Controlled exercise: It is now time to start the tedious part of recovery from tendon strains, and that is a gradually increasing amount of controlled exercise. Two ten minute hand held walks are a good place to start. If the prize pony is a highly strung three quarter fit Thoroughbred who has just had his first two days off in three months and was locked in his box, then it might be worth your while to sedate him for your first few walks.

Surgical treatment: Options include tendon transplantation, carbon fibre implantation and fragment injection, tendon splitting and superior check ligament desmotomy, all of which involve a lengthy period of rest, a fair amount of cost, a graded exercise program and its questionable whether success is due to the surgery or all the other things you do.

3: Remodelling Stage (> day 21)
The main aim of this stage is to guide the repair process to produce a functional tendon i.e. minimise scar tissue, keep the fibres aligned as well as possible and maintain tendon gliding function.

Continue with the laser or therapeutic ultrasound. No need to continue bandaging. Keep confined until around day sixty.

Controlled exercise The regime must be tailored to the individual horse, the severity of the strain and the facilities and time schedule of the owner/carer. Scar tissue reaches 50% of its eventual strength six to eight weeks after the initial injury, so only light exercise until sixty days.

It is essential in the program that every step is a slow and gradual one, so that overloading and fatigue do not occur. Light exercise means up to forty minutes of hand walking. The next step is to ride the horse at the walk for about fifteen minutes a day, this would be at around three months after the initial injury (day 120). Then shortly after starting to ride is a good time to have another ultrasound. At any time during this program if signs of inflammation occur then start anti-inflammatory treatment immediately and organise another ultrasound.

At around three months it is time for the big move to life outside the stable. This is a delicate step as most of our steeds will be dying to buck and gallop around after three months in that tiny stable. So try exercising him as the day before, sedate him and feed him in the small day yard that hopefully you have access to. It is also helpful to have an old ploddy companion pony always within sight to keep him company.

By day 150, hopefully, all going well we are up to about an hour’s walking (now how many walk pirouettes can you practice in an hour!?) then we are allowed trot. Starting at five minutes and adding five minutes every two weeks until day 210 when we can add canter increasing by five minutes every two weeks. By day 270 we can gradually increase to jumping a little bit and by day 330 we can maybe go to a combined training day, where we are sure to win the dressage test because we have had ten months of nothing but flat work!!

Before any step up in the working program it is advisable to check the progress of healing via an ultrasound examination.

The use of hills is a very good way to develop cardiovascular fitness as well as musculoskeletal strength. It removes the need for speed in order to get the heart rate up. This is a good thing as the faster you go the harder it is to judge the onset of your horse’s fatigue and the more likely you are to re-damage the tendon.

Swimming: Swimming is very good for development of cardiovascular fitness but as there is no loading on muscles or tendons it should only be used as well as the above program. Water-treadmills are excellent for rehabilitation after tendon strains but they cost hundreds of thousands and so eliminates use by mere mortals.

As you can see if you have a tendon injury and you want to give it your best shot, then in the next twelve to eighteen months you will turn into a paranoid perfectionist, who times every ride to the second and notices every change in the skin temperature on the back of your pony’s legs. But for the chance of achieving our goals in the sport it is amazing what we’ll do.